A trailing stop and a (normal) stop works completly different. For example on position bought at $10 a stop at say $9 would protect against a loss. A trailing stop of 20% would ensure that you sold if the price drops 20% at any time of the life span on the position. So if the price increased to $20 and drops to $16 it would be sold with a profit of $6.

A normal stop is static protecting against a loss and a trailingstop dynamic and typically primarily used to lock in a profit while keeping the upside of further increases.